Horizontal shaft impact crushers are commonly employed to pulverize many different types of materials including, by way of examples, not limitations, asphalt, concrete, and rock. Such crushers typically include a frame defining a cavity. A rotating impeller driven by an external drive mechanism is disposed within the cavity. The frame includes an opening through which the material to be crushed is inserted into the cavity. One or more breaker plates are generally disposed within the cavity. The rotating impeller repeatedly throws the material to be crushed against the breaker plate(s) thereby breaking the material into small particles.
Horizontal shaft impact crushers generally use a feed plate to help guide the material to be crushed (sometimes referred to as the aggregate) into the hammer circle (i.e., the motion path of the impeller hammers or bars) where it is struck by the impeller bars and crushed. A feed plate is an elongated plate disposed at an angle within the material insertion opening to the cavity of the crusher. The material to be crushed is delivered to the feed plate by a conveyor or the like. The material to be crushed slides down the plate and into the cavity where it is crushed as explained above.
Horizontal shaft impact crushers are generally used to crush a wide range of materials. For example, a crusher may be used to crush asphalt one day, and thereafter be transported to a different site where it is used to crush concrete. Different materials have different physical properties and characteristics that effect their susceptibility to crushing. In view of these differences, applicants have found that it is desirable to insert different materials into crushers at different feed angles. By way of examples, not limitations, concrete and asphalt recycle crushing generally involves large, slabby material that requires a large feed opening to effectively feed the material into the crusher cavity. In contrast, secondary rock crushing involves relatively small uniform material. The crushing of such rock material is generally optimized with a steeper feed angle that allows better penetration into the hammer circle.
Prior art crushers generally employ a single feed plate having a fixed feed angle. This feed angle is generally optimized to work well with one range of material types, but compromises crushing efficiency for other material types.
Feed plates that are removably secured to the frame of an impact crusher are known in the prior art. However, such feed plates are removable to address concerns other than feeding/crushing efficiency such as feed material bridging and assembly considerations. These removable feed plates are not known to have been used in the past to optimize the feed geometry to the properties of the material to be crushed.